Control Apparatus, Fronthaul Multiplexer, Connection Switching Method and Multiplexing Method

The present invention relates to a control device, a fronthaul multiplexer, a connection switching method, and a multiplex method.

11 FIG. 11 FIG. 1 1 1 2 2 3 1 1 1 2 3 3 2 1 1 1 2 is a diagram showing one example of a conventional communication system S. The communication system S includes a plurality of antenna stations-and-, a fronthaul multiplexer, and an aggregation station. The antenna stations-and-are RUs (Radio Unit) in a mobile communication system. The aggregation stationis a CU/DU (Central Unit/Distributed Unit) in the mobile communication system. As shown in, in order to effectively utilize frequency resources of a radio section and the aggregation stationthat performs the base-band processing, a device called a FrontHaul Multiplexer (FHM)is arranged between the antenna stations-and-installed at different locations.

2 1 1 1 2 2 3 2 1 1 1 2 2 1 1 1 2 2 2 The fronthaul multiplexerbehaves in such a way that the plurality of antenna stations-and-connected to the fronthaul multiplexerappears to be one antenna station when viewed from the aggregation station. Specifically, the fronthaul multiplexerperforms signal processing on signals corresponding to the same time point on uplink signals received from the plurality of antenna stations-and-and merges the signals. Depending on a distance between the fronthaul multiplexerand each of the antenna stations-and-, a time point at which each of the uplink signals is received by the fronthaul multiplexerdiffers. For this, the fronthaul multiplexerimparts a delay corresponding to the distance difference to the received uplink signal, merges the signals, and then performs signal processing.

12 FIG. 12 FIG. 2 1 1 2 1 2 2 1 1 1 2 2 1 1 1 2 1 1 2 1 1 1 2 is a diagram for explaining an outline of processing performed by the fronthaul multiplexer. As shown in, it is assumed that the uplink signal transmitted from the antenna station-reaches the fronthaul multiplexerbefore the uplink signal transmitted from the antenna station-depending on the distance between the fronthaul multiplexerand each of the antenna stations-and-. In this case, the fronthaul multiplexeradjusts the receiving time points of the uplink signals transmitted from the respective antenna stations-and-by imparting the delay to the uplink signal transmitted from the antenna station-. Thereafter, the fronthaul multiplexergenerates a multiplex signal by multiplexing the uplink signals transmitted from the respective antenna stations-and-.

2 3 2 3 2 2 In this way, by using the fronthaul multiplexer, the number of required ports for the aggregation stationand the number of required fibers between the fronthaul multiplexerand the aggregation stationcan be reduced. The fronthaul multiplexeradds (or selects) the signal (the one obtained by quantizing the received power) received by the antenna in the uplink direction and makes them appear to be received signals from a single antenna. For this, it is necessary to adjust the sampling time point so that the sampling time point does not deviate at the time of addition. Note that a 5G fronthaul multiplexerhas also been developed.

[NPL 1] “Development of Base Station Device for Introduction of 3.5 GHz Band TD-LTE”, NTT DOCOMO Technical Journal Vol. 24 No. 2

[NPL 2] “5G Network”, NTT DOCOMO Technical Journal, Vol. 28 No. 2

[NPL 3] “Mobile Fronthaul over APN PoC Reference Version 1.0”, Aug. 29, 2022, IOWN GLOBAL FORUM™

By the way, at night when a traffic amount is significantly reduced compared with daytime, power consumed by the aggregation station can be reduced by stopping the aggregation station accommodating an antenna station with a small traffic amount and changing the connection to another aggregation station by switching a route of an optical distribution unit like an optical switch. However, on the assumption that a relationship between the antenna station and the aggregation station is a one-to-one basis, only the location where the aggregation station is provided changes, the number of required aggregation stations does not change, and there is a problem that an effect of power reduction cannot be expected.

In view of the above-described circumstances, an object of the present invention is to provide a technique that can reduce power consumption of an entire system.

One aspect of the present invention is a control device including a sleep detection unit that detects a migration of a communication station, which is connected to a first path via an optical distribution unit that outputs signals outputted from one or more terminal accommodation stations to another path and not via a fronthaul multiplexer that multiplexes and outputs signals outputted from the one or more terminal accommodation stations, to a sleep state among a plurality of communication stations that accommodates the one or more terminal accommodation stations that communicate with a terminal, and a switching signal transmission unit that transmits a switching signal to the optical distribution unit that instructs to switch the terminal accommodation station accommodated in the communication station that has migrated to the sleep state to be accommodated in the communication station connected to a second path via the optical distribution unit and the fronthaul multiplexer when the sleep detection unit detects the migration of the communication station to the sleep state.

One aspect of the present invention is a fronthaul multiplexer in a communication system including a plurality of terminal accommodation stations that communicates with a terminal, an optical distribution unit that outputs each signal outputted from the plurality of terminal accommodation stations to a distribution destination, and a fronthaul multiplexer that multiplexes and outputs each signal outputted from the optical distribution unit, the fronthaul multiplexer includes a switching notification receiving unit that receives information on a delay time required for transfer between the terminal accommodation station to which connection is to be switched and the optical distribution unit and information on the terminal accommodation station to which the connection is to be switched, a delay adjustment unit that adjusts timing at which each signal received via the optical distribution unit is transmitted by imparting a delay to a signal outputted from the terminal accommodation station specified by the information on the terminal accommodation station to which the connection is to be switched on the basis of the information on the delay time received by the switching notification receiving unit, and a signal merging unit that multiplexes and outputs the signal outputted after being adjusted by the delay adjustment unit and the signal outputted from another terminal accommodation station.

One aspect of the present invention is a connection switching method that includes detecting a migration of a communication station, which is connected to a first path via an optical distribution unit that outputs signals outputted from one or more terminal accommodation stations to another path and not via a fronthaul multiplexer that multiplexes and outputs signals outputted from the one or more terminal accommodation stations, to a sleep state among a plurality of communication stations that accommodates the one or more terminal accommodation stations that communicate with a terminal, and transmitting a switching signal to the optical distribution unit that instructs to switch the terminal accommodation station accommodated in the communication station that has migrated to the sleep state to be accommodated in the communication station connected to a second path via the optical distribution unit and the fronthaul multiplexer when detecting the migration of the communication station to the sleep state.

One aspect of the present invention is a multiplex method performed by a fronthaul multiplexer in a communication system including a plurality of terminal accommodation stations that communicates with a terminal, an optical distribution unit that outputs each signal outputted from the plurality of terminal accommodation stations to a distribution destination, and a fronthaul multiplexer that multiplexes and outputs each signal outputted from the optical distribution unit, the multiplex method includes receiving information on a delay time required for transfer between the terminal accommodation station to which connection is to be switched and the optical distribution unit and information on the terminal accommodation station to which the connection is to be switched, adjusting timing at which each signal received via the optical distribution unit is transmitted by imparting a delay to a signal outputted from a terminal accommodation station specified by the information on the terminal accommodation station to which the connection is to be switched on the basis of the information on the received delay time, and multiplexing and outputting the signal outputted after being adjusted and the signal outputted from another terminal accommodation station.

According to the present invention, it is possible to reduce the power consumption of the entire system.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

1 FIG. 1 FIG. 100 100 10 20 30 40 50 100 10 1 10 2 40 1 40 2 10 40 is a diagram showing a configuration example of a communication systemaccording to a first embodiment. The communication systemincludes one or more antenna stations, an optical distribution unit, a fronthaul multiplexer, one or more aggregation stations, and a controller. Althoughshows the case where the communication systemincludes two antenna stations-to-and two aggregation stations-to-, the number of the antenna stationsand aggregation stationsis not particularly limited.

10 1 10 2 10 40 1 40 2 40 10 40 In the following description, the antenna stations-to-are described as the antenna stationif they are not particularly distinguished, and the aggregation stations-to-are described as the aggregation stationif they are not particularly distinguished. Hereinafter, the direction from the antenna stationto the aggregation stationwill be described as the uplink direction.

10 1 10 2 20 20 30 30 40 1 20 40 2 50 20 50 40 1 40 2 An optical transmission line connects the antenna stations-and-to the optical distribution unit, the optical distribution unitto the fronthaul multiplexer, the fronthaul multiplexerto the aggregation station-, and the optical distribution unitto the aggregation station-. The optical transmission line is an optical fiber and transmits an optical signal, for example. An electric line for transmitting an electric signal connects the controllerto the optical distribution unit, and the controllerto the aggregation stations-and-.

1 FIG. 10 1 40 1 20 30 10 2 40 2 20 30 40 1 In, it is assumed that the antenna station-is accommodated in the aggregation station-via the optical distribution unitand the fronthaul multiplexer, and the antenna station-is accommodated in the aggregation station-via the optical distribution unit. The fronthaul multiplexeris accommodated in the aggregation station-.

10 1 2 3 10 1 1 10 2 2 10 10 10 The antenna stationcommunicates with one or more terminals located in cells S, S, and Srepresenting a communication possible range. The antenna station-communicates with one or more terminals located in the cell S, for example. Similarly, the antenna station-communicates with one or more terminals located in the cell S, for example. The antenna stationreceives the uplink signal transmitted from one or more terminals. The antenna stationis an RU in a mobile communication system. The antenna stationis one aspect of a terminal accommodation station.

20 10 20 30 40 2 20 20 10 30 50 20 10 2 40 2 30 20 10 30 20 The optical distribution unithas a plurality of first ports and a plurality of second ports, and is an optical distribution device that outputs the optical signals inputted from one port to another port. The plurality of antenna stationsis connected to the plurality of first ports of the optical distribution unit, and the fronthaul multiplexerand the aggregation station-are connected to the plurality of second ports of the optical distribution unit. The optical distribution unitswitches the connection so that each of the antenna stationsis accommodated in the fronthaul multiplexeraccording to control of the controller. For example, the optical distribution unitswitches the first port to which the antenna station-is connected from the second port to which the aggregation station-is connected to the second port to which the fronthaul multiplexeris connected. Therefore, the optical distribution unitaccommodates each of the antenna stationsin the fronthaul multiplexer. The optical distribution unitmay be an optical switch, a multicast switch, or other switches.

30 10 10 40 30 10 30 30 30 40 1 The fronthaul multiplexerbehaves in such a way that the plurality of connected antenna stationsappears to be one antenna stationwhen viewed from the aggregation station. The fronthaul multiplexerreceives the uplink signal transmitted from each of the antenna stations. The fronthaul multiplexermerges each uplink signal by performing signal processing on the signal corresponding to the same time point to each received uplink signal. Therefore, the fronthaul multiplexergenerates the multiplex signal. The fronthaul multiplexeroutputs the generated multiplex signal to the aggregation station-.

40 1 30 40 1 20 30 40 2 20 40 2 20 30 40 2 50 The aggregation station-processes the multiplex signal output from the fronthaul multiplexeror transfers it to a higher one. In this way, the aggregation station-is connected to a path via the optical distribution unitand the fronthaul multiplexer. The aggregation station-processes the uplink signal transferred from the optical distribution unitor transfers it to a higher one. In this way, the aggregation station-is connected to a path via the optical distribution unitand not via the fronthaul multiplexer. Further, the aggregation station-migrates to a sleep state in response to an instruction from the controller. The sleep state is a function in which power can be saved by stopping some functions.

40 1 40 2 40 30 40 20 30 40 40 1 FIG. The aggregation stations-and-are DUs in the mobile communication system. Althoughshows the case where the number of aggregation stationsconnected to the path via the fronthaul multiplexeris one and the number of aggregation stationsconnected to the path via the optical distribution unitand not via the fronthaul multiplexeris one, the number of aggregation stationsconnected to each path is not particularly limited. The aggregation stationis one aspect of a communication station.

50 100 50 40 40 The controllercontrols the entire communication system. The controlleracquire determination information used for sleep control of the aggregation stationsfrom each of the plurality of aggregation stations. The determination information includes a traffic amount, the number of connected terminals, a traffic distribution amount, an allocation amount, radio quality information such as CQI (Channel Quality Indicator), degree of priority information such as 5QI that communicates, and information on contract services, for example. The following description will be performed on the assumption that the determination material is the traffic amount.

40 50 20 40 40 2 30 50 20 When determined that the aggregation station(hereinafter referred to as “sleep target aggregation station”) to be a sleep target can be migrated to the sleep state on the basis of the determination information, the controllerinstructs the optical distribution unitto switch. The sleep target aggregation station is the aggregation station(for example, aggregation station-) that is not connected to a path via the fronthaul multiplexer, for example. The controllerinstructs the sleep target aggregation station to sleep before switching of the optical distribution unitor after switching.

30 50 30 30 31 32 Next, the functions included in the fronthaul multiplexerand the controllerwill be described in detail. First, the functions of the fronthaul multiplexerwill be described. The fronthaul multiplexerincludes a lower-side delay insertion unitand a signal merging unit.

31 20 31 31 The lower-side delay insertion unitreceives each uplink signal transferred from the optical distribution unit. The lower-side delay insertion unitimparts a delay to at least some of the received uplink signals to make them signals received at the same time point. Here, imparting a delay means inserting a delay to a signal and delaying it. The lower-side delay insertion unitimparts the delay corresponding to the distance difference to the uplink signal, for example.

32 31 The signal merging unitgenerates the multiplex signal by multiplexing each uplink signal including the uplink signal to which the delay is imparted by the lower-side delay insertion unit.

50 50 51 52 53 54 Next, the functions included in the controllerwill be described. The controllerincludes an acquisition unit, a sleep control unit, a sleep detection unit, and a switching signal transmission unit.

51 40 51 40 51 40 52 The acquisition unitacquires the determination information from each of the plurality of aggregation stations. The acquisition unitacquires the determination information from each of the plurality of aggregation stationsat predetermined timing or periodically, for example. The acquisition unitoutputs the acquired determination information of each aggregation stationto the sleep control unit.

52 40 40 51 52 The sleep control unitdetermines whether or not the aggregation stationcan be asleep on the basis of the determination information of each aggregation stationacquired by the acquisition unit. The sleep control unitdetermines whether or not the sleep target aggregation station can be asleep, for example.

52 40 When the determination information is the traffic amount, the sleep control unitdetermines that the sleep target aggregation station can be asleep when the traffic amount of the sleep target aggregation station remains less than a first threshold value for a predetermined period of time or longer and when another aggregation stationcan accommodate the traffic of the sleep target aggregation station.

52 52 52 40 On the other hand, the sleep control unitdetermines that the sleep target aggregation station cannot be asleep when the traffic amount of the sleep target aggregation station is equal to or greater than the first threshold value. Alternatively, the sleep control unitmay determine that the sleep target aggregation station cannot be asleep when the period in which the traffic amount of the sleep target aggregation station becomes less than the first threshold value does not continue for the predetermined period or longer. Alternatively, the sleep control unitmay determine that the sleep target aggregation station cannot be asleep when another aggregation stationcannot accommodate the traffic of the sleep target aggregation station even if the period in which the traffic amount of the sleep target aggregation station becomes less than the first threshold value continues for the predetermined period or longer.

52 10 40 When the determination information is the number of connection terminals, the sleep control unitdetermines that the sleep target aggregation station can be asleep when the number of connection terminals (for example, the number of antenna stations) of the sleep target aggregation station is less than a predetermined criterion and another aggregation stationcan accommodate the connection terminals of the sleep target aggregation station.

52 52 40 On the other hand, the sleep control unitdetermines that the sleep target aggregation station cannot be asleep when the number of connection terminals of the sleep target aggregation station is equal to or greater than the predetermined criterion. Alternatively, the sleep control unitmay determine that the sleep target aggregation station cannot be asleep when another aggregation stationcannot accommodate the connection terminals of the sleep target aggregation station even if the number of connection terminals of the sleep target aggregation station becomes less than the predetermined criterion.

52 53 52 When determining that the sleep is possible, the sleep control unitnotifies the sleep detection unitto make the sleep target aggregation station asleep. Further, when determining that the sleep is possible, the sleep control unittransmits a sleep instruction to the sleep target aggregation station. The sleep instruction is an instruction for executing the migration to the sleep state.

53 52 53 40 2 20 30 The sleep detection unitdetects the migration of the sleep target aggregation station to the sleep state in response to the notification from the sleep control unit. The sleep detection unitdetects the migration of the aggregation station-connected to the path via the optical distribution unitand not via the fronthaul multiplexerto the sleep state, for example.

53 54 10 20 40 54 20 When the sleep detection unitdetects the migration of the sleep target aggregation station to the sleep state, the switching signal transmission unittransmits a switching signal including an instruction to switch an accommodation destination of the antenna stationto the optical distribution unit. The switching signal includes information indicating the port to which the aggregation stationto be the switching destination is connected, for example. The switching signal transmission unitacquires information included in the switching signal from the optical distribution unit connection table, for example. The optical distribution unit connection table is a table in which information about the connection of the optical distribution unitis registered. The details of the optical distribution unit connection table will be described later. The optical distribution unit connection table is stored in a memory that is not shown by drawings.

54 20 10 40 20 30 When the migration of the sleep target aggregation station to the sleep state is detected, the switching signal transmission unittransmits the switching signal to the optical distribution unitthat instructs to switch the antenna stationaccommodated in the sleep target aggregation station to be accommodated by the aggregation stationconnected to the path via the optical distribution unitand the fronthaul multiplexer, for example.

2 FIG. 20 20 20 10 20 is a diagram showing a configuration example of the optical distribution unit connection table according to the first embodiment. The optical distribution unit connection table has a plurality of records in which information about the connection of the optical distribution unitis registered. Each record has values of a lower device, a lower device connection port, a higher device, a higher device connection port, a port used at sleep, an aggregation station used at sleep, a port used at sleep release, and a corresponding aggregation station at sleep release. The lower device represents a lower device connected to the optical distribution unit. The lower device connected to the optical distribution unitis the antenna station, for example. The lower device connection port represents the first port of the optical distribution unitto which the lower device is connected.

20 20 40 20 20 10 40 40 10 40 20 10 40 40 10 40 A higher device represents a higher device connected to the optical distribution unit. The higher device connected to the optical distribution unitis the aggregation station, for example. The higher device connection port represents the second port of the optical distribution unitto which the higher device is connected. The port used at sleep represents the second port of the optical distribution unitused as a connection destination of the antenna stationwhen the aggregation stationis asleep. The aggregation station used at sleep represents the aggregation stationused as a connection destination of the antenna stationwhen the aggregation stationis asleep. The port used at sleep release represents the second port of the optical distribution unitused as a connection destination of the antenna stationwhen the aggregation stationreleases the sleep. The corresponding aggregation station at sleep release represents the aggregation stationused as a connection destination of the antenna stationwhen the aggregation stationreleases the sleep.

3 FIG. 3 FIG. 3 FIG. 20 20 1 4 1 4 30 1 2 1 20 30 is a diagram for explaining the switching of the connection relationship of the optical distribution unitaccording to the first embodiment. In, as one example, a configuration is described, in which the optical distribution unithas four first ports dto dand four second ports uto u, and the fronthaul multiplexerhas two first ports pto pand one second port q. Note that the number of ports included in the optical distribution unitand the fronthaul multiplexeris not limited to the example shown in.

3 FIG. 10 1 1 20 10 2 2 20 30 1 2 20 40 2 3 20 20 1 2 30 40 1 1 30 20 1 1 2 3 As shown in, the antenna station-is connected to the first port dof the optical distribution unit, the antenna station-is connected to the first port dof the optical distribution unit, the fronthaul multiplexeris connected to the second ports uand uof the optical distribution unit, and the aggregation station-is connected to the second port uof the optical distribution unit. The optical distribution unitis connected to the first ports pand pof the fronthaul multiplexer, and the aggregation station-is connected to the second port qof the fronthaul multiplexer. Inside the optical distribution unit, the first port dand the second port uare connected, and the first port dand the second port uare connected.

20 53 40 2 54 40 2 3 20 54 10 2 40 2 2 20 3 FIG. 2 FIG. Here, a flow of connection switching of the optical distribution unitby using the connection relationship shown inas an example will be described using the optical distribution unit connection table shown in. When the sleep detection unitdetects the migration of the aggregation station-to the sleep state, the switching signal transmission unitrefers to the optical distribution unit connection table to grasp that the aggregation station-is connected to the second port uof the optical distribution unit. Further, the switching signal transmission unitgrasps that the antenna station-accommodated in the aggregation station-is connected to the first port dof the optical distribution unit.

54 10 2 40 1 2 20 40 1 40 2 54 2 20 3 20 2 20 2 20 54 20 20 2 2 3 FIG. Thereafter, the switching signal transmission unitrefers to the items of the port used at sleep and the aggregation station used at sleep in the optical distribution unit connection table to grasp that the connection destination of the antenna station-is the aggregation station-and utilization of the second port uof the optical distribution unittoward the aggregation station-when the aggregation station-is asleep. Therefore, the switching signal transmission unitgenerates the switching signal instructing to switch the connection connected from the first port dof the optical distribution unitto the second port uof the optical distribution unitto a connection connected from the first port dof the optical distribution unitto the second port uof the optical distribution unit. The switching signal transmission unittransmits the generated switching signal to the optical distribution unit. Therefore, the optical distribution unitswitches the connection so as to connect the first port dand the second port uas shown by a dotted line in.

4 FIG. 4 FIG. 7 FIG. 100 40 1 40 2 40 1 40 2 10 1 40 1 20 30 10 2 40 2 20 10 40 2 10 2 40 2 40 2 is a sequence diagram showing a flow of processing of the communication systemaccording to the first embodiment. In, the aggregation stations-and-are collectively described as aggregation station group, but will be described as aggregation station-or-as needed. At the start of the processing in, it is assumed that the antenna station-is connected to the aggregation station-via the optical distribution unitand the fronthaul multiplexer, and the antenna station-is connected to the aggregation station-via the optical distribution unit. As one example, it is assumed thatterminal devices are connected to the aggregation station-via the antenna station-, and the total traffic amount passing through the aggregation station-flows by 10% or more of the amount (for example, 1 Gbps) that can be processed by the aggregation station-.

51 50 101 40 2 10 2 51 40 40 2 40 1 40 2 51 40 52 The acquisition unitof the controlleracquires information on the traffic amount of each aggregation station 40 (step S). Note that, it is assumed that the number of terminal devices connected to the aggregation station-via the antenna station-is two before the acquisition unitacquires the information on the traffic amount of each aggregation station. Therefore, it is assumed that the average traffic flowing through the aggregation stations-is 5%=50 Mbps or less of the traffic that can be processed by the aggregation stations-and-. The acquisition unitoutputs the acquired information on the traffic amount of each aggregation stationto the sleep control unit.

52 40 51 102 52 40 2 40 2 52 40 2 52 40 2 203 40 2 The sleep control unitdetermines whether or not to allow sleep on the basis of the information on the traffic amount of each aggregation stationoutputted from the acquisition unit(step S). For example, the sleep control unitdetermines whether or not the aggregation station-can be asleep on the basis of information on the traffic amount of the aggregation station-. Here, it is assumed that the sleep control unitdetermines that the aggregation station-can be asleep. In this case, the sleep control unittransmits the sleep instruction to the aggregation station-(step S). Therefore, the aggregation station-can be migrated to the sleep state.

40 2 20 10 2 40 2 52 40 2 20 Note that if the aggregation station-is migrated to the sleep state before the optical distribution unitperforms the switching, signals transmitted from the antenna station-which is connected to the aggregation station-could be lost. Thus, the sleep control unitmay transmit the sleep instruction to the aggregation station-after switching is performed by the optical distribution unit.

52 53 40 2 53 40 2 52 53 40 2 104 53 20 40 2 Further, the sleep control unitnotifies the sleep detection unitto make the aggregation station-asleep. The sleep detection unitdetects the migration of the aggregation station-to the sleep state by the notification from the sleep control unit. The sleep detection unitdetermines that the switching is required in accordance with the detection of the migration of the aggregation station-to the sleep state (step S). The sleep detection unitnotifies that the connection switching of the optical distribution unitis necessary and that the aggregation station-migrates to the sleep state.

54 53 54 2 20 3 20 2 20 2 20 54 20 105 The switching signal transmission unitgenerates the switching signal in response to the notification from the sleep detection unit. Specifically, the switching signal transmission unitrefers to the optical distribution unit connection table to generate the switching signal that instructs to switch the connection connected from the first port dof the optical distribution unitto the second port uof the optical distribution unitto the connection from the first port dof the optical distribution unitto the second port uof the optical distribution unit. The switching signal transmission unittransmits the generated switching signal to the optical distribution unit(step S).

20 50 20 106 20 2 2 10 1 10 2 40 1 10 1 10 2 The optical distribution unitreceives the switching signal transmitted from the controller. The optical distribution unitswitches the connection between ports on the basis of the received switching signal (step S). For example, the optical distribution unitswitches the connection so as to connect the first port dand the second port u. By switching the connection, the antenna stations-and-are accommodated in the aggregation station-. Thereafter, it is assumed that the uplink signal is transmitted from each of the antenna stations-and-.

20 10 1 10 2 20 10 1 10 2 30 20 30 The optical distribution unitinputs the uplink signals transmitted from each of the antenna stations-and-from the first port, and outputs the inputted uplink signals from the second port. The first port of the optical distribution unitto which the antenna stations-and-are connected, respectively, is connected to the second port to which the fronthaul multiplexeris connected. Therefore, each uplink signal inputted to the optical distribution unitis transferred to the fronthaul multiplexer.

30 20 10 1 30 10 2 30 10 1 10 2 10 1 10 2 30 The fronthaul multiplexerreceives each uplink signal transferred from the optical distribution unit. The distance from the antenna station-to the fronthaul multiplexeris often different from the distance from the antenna station-to the fronthaul multiplexerand the antenna stations-and-transmit uplink signals at different timing, respectively. For this, the uplink signals transmitted from the respective antenna stations-and-are received at different timing in the fronthaul multiplexer.

31 30 108 31 32 32 31 109 32 40 1 110 40 1 20 40 1 The lower-side delay insertion unitof the fronthaul multiplexerinserts a delay into some of each of the received uplink signals (step S). Note that the insertion of the delay is the same as that in the prior art. The lower-side delay insertion unitoutputs each uplink signal including the uplink signal to which the delay is imparted to the signal merging unit. The signal merging unitmultiplexes each uplink signal including the uplink signal to which the delay is imparted by the lower-side delay insertion unitto generate a multiplex signal (step S). The signal merging unitoutputs the generated multiplex signal to the aggregation station-(step S). The aggregation station-receives the multiplex signal outputted from the optical distribution unit. Thereafter, the aggregation station-processes the received multiplex signal or transfers it to the higher one.

100 53 40 2 20 30 40 54 20 10 2 40 2 40 20 30 53 40 2 The communication systemconfigured as described above includes the sleep detection unitthat detects the migration of the aggregation station-connected to the first path via the optical distribution unitand not via the fronthaul multiplexerto the sleep state among the plurality of aggregation stationsand the switching signal transmission unitthat transmits the switching signal to the optical distribution unitthat instructs to switch the antenna station-accommodated in the aggregation station-that has migrated to the sleep state to be accommodated in the aggregation stationconnected to the second path via the optical distribution unitand the fronthaul multiplexerwhen the sleep detection unitdetects the migration of the aggregation station-to the sleep state.

40 10 40 40 30 20 30 10 1 10 2 40 1 40 10 10 40 30 10 40 40 1 40 2 40 10 In this way, when the load on the aggregation stationis reduced to allow sleep (for example, traffic amount is reduced), the connection is switched so that the antenna stationconnected to the aggregation stationthat can sleep is accommodated in the aggregation stationconnected to the fronthaul multiplexer. After switching the connection by the optical distribution unit, the delay insertion and signal merging are performed through the fronthaul multiplexer, so that the signals of the antenna station-and the antenna station-are multiplexed and accommodated in one port of the aggregation station-. Accordingly, when the load on the aggregation stationconnected to the antenna stationon a one-to-one basis decreases, the signal processing of the antenna stationcan be aggregated to the aggregation stationconnected to the fronthaul multiplexerfor multiplexing signals of the plurality of antenna stations. Therefore, it is not necessary to prepare extra ports or other aggregation stationsadditionally on the aggregation station-side. For this, the aggregation station-can be allowed to sleep, and power consumption of the entire system can be reduced as compared with switching the aggregation stationconnected to the antenna stationin a one-to-one basis.

40 30 Further, since the switching is performed when the load on the aggregation stationis low enough to allow sleep, the influence of depletion of the band on the user can be reduced even after the aggregation via the fronthaul multiplexeris performed.

50 20 20 100 100 10 20 30 40 60 65 100 10 1 10 2 40 1 40 2 10 40 5 FIG. 5 FIG. a a a In the above-mentioned embodiment, the controllerdetermines whether or not to allow the sleep and issues the switching instruction to the optical distribution unit. It may be configured to determine whether or not to allow the sleep and issue the switching instruction to the optical distribution unitby different devices.is a diagram showing a configuration example of a communication systemaccording to a modification example of the first embodiment. The communication systemincludes one or more antenna stations, an optical distribution unit, a fronthaul multiplexer, one or more aggregation stations, a radio controller, and an optical distribution unit controller. Althoughshows the case where the communication systemincludes two antenna stations-to-and two aggregation stations-to-, the number of the antenna stationsand aggregation stationsis not particularly limited.

100 100 60 65 50 100 100 60 40 65 60 51 52 a a The communication systemis different in configuration from the communication systemin that it includes the radio controllerand the optical distribution unit controllerin place of the controller. The other configurations of the communication systemare the same as those of the communication system. Hereinafter, the difference will be mainly described. The radio controllerperforms radio communication with the aggregation stationand with the optical distribution unit controller. The radio controllerincludes an acquisition unitand a sleep control unit.

51 60 40 51 40 51 40 52 52 60 40 40 51 The acquisition unitincluded in the radio controlleracquires the determination information from each of the plurality of aggregation stationsby radio. The acquisition unitacquires the determination information from each of the plurality of aggregation stationsat predetermined timing or periodically by radio, for example. The acquisition unitoutputs the acquired determination information of each aggregation stationto the sleep control unit. The sleep control unitincluded in the radio controllerdetermines whether or not the aggregation stationcan be asleep on the basis of the determination information of each aggregation stationacquired by the acquisition unit.

52 65 52 When determined to allow sleep, the sleep control unitnotifies the optical distribution unit controllerthat the sleep target aggregation station is made asleep by radio. Further, when determined to allow sleep, the sleep control unittransmits the sleep instruction to the sleep target aggregation station by radio.

65 20 65 53 54 53 65 60 53 54 65 20 20 54 The optical distribution unit controllercontrols the optical distribution unit. The optical distribution unit controllerincludes a sleep detection unitand a switching signal transmission unit. The sleep detection unitincluded in the optical distribution unit controllerdetects the migration of the sleep target aggregation station to the sleep state in response to the notification from the radio controller. When the sleep detection unitdetects the migration of the sleep target aggregation station to the sleep state, the switching signal transmission unitincluded in the optical distribution unit controllertransmits the switching signal to the optical distribution unit. The switching operations of the optical distribution unitby the switching signal transmission unitis the same as the method shown in the first embodiment.

50 40 40 2 In a second embodiment, a configuration of the case where the sleeping aggregation station is released from sleeping will be described. A system configuration and a device configuration according to the second embodiment are the same as those of the first embodiment. The difference from the first embodiment is the operation of the controller. Hereinafter, the difference will be mainly described. Note that, in the second embodiment, it is assumed that at least one aggregation station(for example, aggregation station-) is in the sleep state.

52 40 40 51 40 The sleep control unitdetermines whether or not the sleep release of the sleeping aggregation stationis required on the basis of the determination information on each aggregation stationacquired by the acquisition unit. Hereinafter, the aggregation stationthat is a sleep release target is referred to as a sleep release target aggregation station.

52 40 40 52 When the determination information is the traffic amount, the sleep control unitdetermines that the sleep release of the sleep release target aggregation station is required when the traffic amount of the aggregation stationthat is not in the sleep state becomes a second threshold value or more. On the other hand, when the traffic amount of the aggregation stationthat is not in the sleep state is less than the second threshold value, the sleep control unitdetermines that the sleep release of the sleep release target aggregation station is not required.

52 10 40 40 52 When the determination information is the number of connection terminals, the sleep control unitdetermines that the sleep release of the sleep release target aggregation is required when the number of connection terminals (for example, the number of antenna stations) of the aggregation stationthat is not in the sleep state becomes a predetermined criterion or more. On the other hand, when the number of connection terminals of the aggregation stationthat is not in the sleep state is less than the predetermined criterion, the sleep control unitdetermines that the sleep release of the sleep release target aggregation station is not required.

52 53 52 When determined that the sleep release is required, the sleep control unitnotifies the sleep detection unitthat the sleep release of the sleep release target aggregation station starts. Further, when determined that the sleep release is required, the sleep control unittransmits the sleep release instruction to the sleep release target aggregation station. The sleep release instruction is an instruction to release the sleep state.

53 52 53 40 2 20 30 The sleep detection unitdetects the start of the sleep release of the sleep release target aggregation station in response to the notification from the sleep control unit. The sleep detection unitdetects the start of the sleep release of the aggregation station-connected to the path via the optical distribution unitand not via the fronthaul multiplexer, for example.

53 54 10 20 54 When the sleep detection unitdetects the start of the sleep release of the sleep release target aggregation station, the switching signal transmission unittransmits the switching signal including the instruction to switch the accommodation destination of the antenna stationto the optical distribution unit. The switching signal transmission unitacquires information included in the switching signal from the optical distribution unit connection table, for example.

54 20 10 40 40 20 30 When the start of sleep release of the sleep release target aggregation station is detected, the switching signal transmission unittransmits the switching signal to the optical distribution unitthat instructs to switch the antenna stationaccommodated in the aggregation stationthat is not sleeping to be accommodated in the aggregation stationconnected to the path via the optical distribution unitand not via the fronthaul multiplexer.

6 FIG. 6 FIG. 3 FIG. 20 1 2 2 20 is a diagram for explaining the switching of the connection relationship of the optical distribution unitaccording to the second embodiment. In, the difference fromis that the first port dl and the second port uare connected to each other and the first port dand the second port uare connected to each other inside the optical distribution unit.

20 53 40 2 54 40 2 3 20 54 10 2 2 20 6 FIG. 2 FIG. Here, a flow of connection switching of the optical distribution unitby using the connection relationship shown inas an example will be described using the optical distribution unit connection table shown in. When the sleep detection unitdetects the start of the sleep release of the aggregation station-, the switching signal transmission unitrefers to the optical distribution unit connection table to grasp that the aggregation station-is connected to the second port uof the optical distribution unit. Further, the switching signal transmission unitgrasps that the antenna station-is connected to the first port dof the optical distribution unit.

54 10 2 40 2 3 20 40 2 40 2 54 2 20 2 20 2 20 3 20 54 20 20 2 3 6 FIG. Thereafter, the switching signal transmission unitrefers to the items of the port used at sleep release and the corresponding aggregation station at sleep release in the optical distribution unit connection table to grasp that the connection destination of the antenna station-is the aggregation station-and the second port uof the optical distribution unittoward the aggregation station-is utilized when the sleep of the aggregation station-is released. Therefore, the switching signal transmission unitgenerates the switching signal that instructs to switch the connection connected from the first port dof the optical distribution unitto the second port uof the optical distribution unitto a connection connected from the first port dof the optical distribution unitto the second port uof the optical distribution unit. The switching signal transmission unittransmits the generated switching signal to the optical distribution unit. Therefore, the optical distribution unitswitches connection so as to connect the first port dand the second port uas shown by a dotted line in.

100 20 10 2 40 2 40 2 40 1 According to the communication systemaccording to the second embodiment configured as described above, after the optical distribution unitswitches the connection, the antenna station-is connected to the aggregation station-again, so that the frequency resource of the aggregation station-which is not shared with the aggregation station-can be used. For this, even if the number of accommodated terminals increases, or a terminal with a large amount of communication or a terminal requiring low delay is accommodated, the service request can be satisfied.

30 Further, since it is possible to dynamically change whether or not to perform port aggregation to the fronthaul multiplexerdepending on the utilization situation, both efficient (high power efficiency) service provision and wide-band service provision can be achieved.

50 20 20 100 60 65 50 60 40 65 60 51 52 In the above-mentioned embodiment, the controllerdetermines whether or not the sleep release is required and issues the switching instruction to the optical distribution unit. It may be configured to determine whether or not the sleep release is required and issue the switching instruction to the optical distribution uniton different devices. When configured in this way, the communication systemaccording to the second embodiment includes a radio controllerand an optical distribution unit controllerin place of the controllersimilarly to the modification example of the first embodiment. The radio controllerperforms radio communication with the aggregation stationand with the optical distribution unit controller. The radio controllerincludes an acquisition unitand a sleep control unit.

51 60 40 51 40 51 40 52 52 60 40 51 52 65 52 The acquisition unitincluded in the radio controlleracquires the determination information from each of the plurality of aggregation stationsby radio. The acquisition unitacquires the determination information from each of the plurality of aggregation stationsat predetermined timing or periodically by radio, for example. The acquisition unitoutputs the acquired determination information of each aggregation stationto the sleep control unit. The sleep control unitincluded in the radio controllerdetermines whether or not the sleep release of the sleep release target aggregation station is required on the basis of the determination information of each aggregation stationacquired by the acquisition unit. When determined that the sleep release is required, the sleep control unitnotifies the optical distribution unit controllerthat the sleep release of the sleep release target aggregation station starts by radio. Further, when determined that the sleep release is required, the sleep control unittransmits the sleep release instruction to the sleep release target aggregation station by radio.

65 20 65 53 54 53 65 60 53 54 65 20 20 54 The optical distribution unit controllercontrols the optical distribution unit. The optical distribution unit controllerincludes a sleep detection unitand a switching signal transmission unit. The sleep detection unitincluded in the optical distribution unit controllerdetects the start of sleep release of the sleep release target aggregation station in response to the notification from the radio controller. When the sleep detection unitdetects the start of the sleep release target aggregation station, the switching signal transmission unitincluded in the optical distribution unit controllertransmits the switching signal to the optical distribution unit. The switching operation of the optical distribution unitby the switching signal transmission unitis the same as the method shown in the second embodiment.

In the first embodiment, when changing the aggregation station accommodating the antenna station to another aggregation station by switching the optical distribution unit, link disconnection occurs. Then, the distance between the antenna station and the aggregation station before the switching and the distance between the antenna station and the aggregation station after the switching are changed, so that the procedure for establishing the link including the delay measurement needs to be performed again between the antenna station and the aggregation station after the switching. For this, there is a problem that communication is disconnected during this period. Thus, in the third embodiment, a configuration for solving this problem will be described.

7 FIG. 7 FIG. 100 100 10 20 30 40 50 100 10 1 10 3 40 1 40 2 10 40 b b b b b is a diagram showing a configuration example of a communication systemaccording to a third embodiment. The communication systemincludes one or more antenna stations, an optical distribution unit, a fronthaul multiplexer, one or more aggregation stations, and a controller. Althoughshows the case where the communication systemincludes three antenna stations-to-and two aggregation stations-to-, the number of the antenna stationsand aggregation stationsis not particularly limited.

10 1 10 2 10 3 20 20 30 30 40 1 20 40 2 40 3 50 20 50 30 50 40 1 40 2 b b b b b b An optical transmission line connects the antenna stations-,-, and-to the optical distribution unit, the optical distribution unitto the fronthaul multiplexer, the fronthaul multiplexerto the aggregation station-, and the optical distribution unitto the aggregation stations-and-. An electric line for transmitting electric signals connects the controllerand the optical distribution unit, the controllerand the fronthaul multiplexer, and the controllerand the aggregation stations-and-.

7 FIG. 10 1 40 1 20 30 10 2 10 3 40 2 40 3 20 30 40 1 b b In, it is assumed that the antenna station-is accommodated in the aggregation station-via the optical distribution unitand the fronthaul multiplexer, and the antenna stations-and-are accommodated in the aggregation stations-and-via the optical distribution unit. The fronthaul multiplexeris accommodated in the aggregation station-.

100 100 30 50 30 50 10 40 100 100 b b b b The communication systemis different in configuration from the communication systemin that it includes a fronthaul multiplexerand a controllerin place of the fronthaul multiplexerand the controller, and in that it includes three antenna stationsand aggregation stations. The other configurations of the communication systemare the same as those of the communication system. Hereinafter, the difference will be mainly described.

50 100 50 40 40 50 10 30 20 50 10 40 20 30 10 1 30 10 1 40 1 10 10 1 40 20 30 20 b b b b b b b The controllercontrols the entire communication system. The controlleracquires determination information used for sleep control of the aggregation stationfrom each of the plurality of aggregation stations. Further, the controlleracquires the delay time (hereinafter referred to as “lower delay time”) from the antenna stationwhose connection destination is switched to the fronthaul multiplexerin advance in response to the switching of the connection relationship by the optical distribution unit. Here, the acquisition target of the lower delay time by the controlleris the antenna stationwhere a new connection destination is connected to the aggregation stationvia the optical distribution unitand the fronthaul multiplexer. This is because the lower delay time between the antenna station-and the fronthaul multiplexeris measured since the communication is performed between the antenna station-and the aggregation station-in the antenna station(for example, the antenna station-) connected to the aggregation stationvia the optical distribution unitand the fronthaul multiplexerbefore the optical distribution unitperforms the connection switching.

7 FIG. 10 2 10 3 40 20 30 10 2 10 3 30 10 2 10 3 50 50 30 30 10 50 b b b b b b. In the example shown in, the antenna stations-and-are connected to the aggregation stationconnected to the path via the optical distribution unitand not via the fronthaul multiplexer. For this, the lower delay time between each of the antenna stations-and-and the fronthaul multiplexeris not measured. Thus, the antenna stations-and-are the targets of acquiring the lower delay time by the controller. The controllernotifies the fronthaul multiplexerof the acquired information on the lower delay time. Therefore, the fronthaul multiplexerdoes not need to measure the delay time with the newly connected antenna stationagain by recycling the value of the lower delay time notified from the controller

30 10 10 40 30 10 30 30 30 40 1 b b b b b The fronthaul multiplexerbehaves in such a way that the plurality of connected antenna stationsappears to be one antenna stationwhen viewed from the aggregation station. The fronthaul multiplexerreceives the uplink signal transmitted from each of the antenna stations. The fronthaul multiplexermerges each uplink signal by performing signal processing on the signal corresponding to the same time point on each received uplink signal. Therefore, the fronthaul multiplexergenerates the multiplex signal. The fronthaul multiplexeroutputs the generated multiplex signal to the aggregation station-.

30 50 30 10 10 30 30 30 b b b b b b The fronthaul multiplexeracquires information on the lower delay time from the controllerin advance when imparting the delay to each uplink signal. Then, the fronthaul multiplexeracquires the delay time to be imparted to the uplink signal transmitted from each of the antenna stationson the basis of the acquired information on the lower delay time. As mentioned above, the lower delay time is the delay time between the antenna stationand the fronthaul multiplexer. The fronthaul multiplexeracquires the delay time to be imparted to each uplink signal for each uplink signal so that the same delay is obtained by taking into account the lower delay time in order to add or select signals corresponding to the same time point when merging each uplink signal. Then, the fronthaul multiplexercan merge each uplink signal by imparting the acquired delay time to each uplink signal.

30 50 30 30 31 32 33 b b b b b Next, the functions included in the fronthaul multiplexerand the controllerwill be described in detail. First, the functions included in the fronthaul multiplexerwill be described. The fronthaul multiplexerincludes a lower-side delay insertion unit, a signal merging unit, and a switching notification receiving unit.

33 10 30 50 33 10 30 33 31 10 b b b b The switching notification receiving unitreceives information on the lower delay time corresponding to the antenna station(hereinafter referred to as “a switching target antenna station”) newly connected to the fronthaul multiplexerfrom the controller. The switching notification receiving unitacquire the delay time to be imparted to the uplink signal transmitted from each of the antenna stationsconnected to the fronthaul multiplexeron the basis of the received information on the lower delay time and the insertion delay table. Hereinafter, the delay time to be imparted to the uplink signal will be referred to as the insertion delay time. The insertion delay table is a table in which information about insertion delay time is registered. The details of the insertion delay table will be described later. The insertion delay table is stored in a memory that is not shown by drawings. The switching notification receiving unitnotifies the lower-side delay insertion unitof the acquired information on the insertion delay time of each antenna station.

31 20 31 33 31 10 b b b The lower-side delay insertion unitreceives each uplink signal transferred from the optical distribution unit. The lower-side delay insertion unitimparts the delay value indicated by information on the delay time notified from the switching notification receiving unitto at least some of the received uplink signals. Therefore, the lower-side delay insertion unitcan make each uplink signal transmitted from the different antenna stationa signal received at the same time point.

50 50 51 52 53 54 55 b b Next, the functions included in the controllerwill be described. The controllerincludes an acquisition unit, a sleep control unit, a sleep detection unit, a switching signal transmission unit, and a delay time management unit.

53 55 55 30 55 20 b When the sleep detection unitdetects the migration of the sleep target aggregation station to the sleep state, the delay time management unitacquires information on the lower delay time corresponding to the switching target antenna station. The delay time management unitmay calculate the lower delay time from a measurement value using an AMCC (Auxiliary Management and Control Channel) or may hold a value once measured in the past in the fronthaul multiplexer. Note that, in the case of using AMCC, the delay time management unitsends a delay measurement signal to the switching target antenna station to measure the propagation delay between the optical distribution unitand the switching target antenna station, and holds the value obtained by halving the round-trip delay time as the one-way delay, for example.

54 20 55 33 30 When the switching signal transmission unitsends the switching signal to the optical distribution unit, the delay time management unitnotifies the switching notification receiving unitof the fronthaul multiplexerthat the switching target antenna station is connected and the information on the delay time corresponding to the switching target antenna station to be connected from now.

8 FIG. 2 FIG. is a diagram showing a configuration example of an optical distribution unit connection table according to the third embodiment. Note that since each value registered in the optical distribution unit connection table is the same as that described in, description thereof will be omitted.

9 FIG. 30 30 10 30 b b b is a diagram showing a configuration example of the insertion delay table according to the third embodiment. The insertion delay table has a plurality of records in which information about the insertion delay time is registered. Each record has values of the lower device, lower device connection port, lower delay time, and insertion delay time. The lower device in the insertion delay table represents lower device connected to the fronthaul multiplexer. The lower device connected to the fronthaul multiplexeris the antenna station, for example. The lower device connection port represents the first port of the fronthaul multiplexerto which the lower device is connected.

10 30 10 1 10 2 10 3 30 55 10 1 10 2 10 3 b b 9 FIG. 9 FIG. The lower delay time represents a delay time required for transmission between the antenna stationand the fronthaul multiplexer. The insertion delay time represents the delay time to be imparted to the uplink signal. As shown in, it is assumed that the lower delay time from each of the antenna stations-,-, and-to the fronthaul multiplexeris 15 us, 30 us, and 50 us. The delay time management unitacquires the insertion delay time based on the lower delay time so that the total value of the lower delay time and the insertion delay time becomes the same value (so that they become the same delay) in each of the antenna stations-,-, and-. For example,shows an example in which the insertion delay time is acquired so that the total value becomes 100 us.

10 FIG. 10 FIG. 10 FIG. 20 20 1 4 1 4 30 1 2 1 20 30 b b is a diagram for explaining the switching of the connection relationship of the optical distribution unitaccording to the third embodiment. In, as one example, a configuration will be described, in which the optical distribution unithas four first ports dto dand four second ports uto uand the fronthaul multiplexerhas two first ports pto pand one second port q. Note that the number of ports included in the optical distribution unitand the fronthaul multiplexeris not limited to the example shown in.

10 FIG. 10 1 1 20 10 2 3 20 10 4 4 20 30 1 2 20 40 2 3 20 40 3 4 20 b As shown in, the antenna station-is connected to the first port dof the optical distribution unit, the antenna station-is connected to the first port dof the optical distribution unit, and the antenna station-is connected to the first port dof the optical distribution unit. Further, the fronthaul multiplexeris connected to the second ports uand uof the optical distribution unit, the aggregation station-is connected to the second port uof the optical distribution unit, and the aggregation station-is connected to the second port uof the optical distribution unit.

20 1 2 30 40 1 1 30 20 1 1 3 3 4 4 b b The optical distribution unitis connected to the first ports pand pof the fronthaul multiplexer, and the aggregation station-is connected to the second port qof the fronthaul multiplexer. Inside the optical distribution unit, the first port dand the second port uare connected, the first port dand the second port uare connected, and the first port dand the second port uare connected.

20 53 40 3 55 10 3 40 3 30 10 3 40 3 30 55 10 FIG. 8 FIG. 9 FIG. b b Here, the flow of connection switching of the optical distribution unitby using the connection relationship shown inas an example will be described using the optical distribution unit connection table shown inand the insertion delay table shown in. When the sleep detection unitdetects the migration of the aggregation station-to the sleep state, the delay time management unitrefers to the insertion delay table to judge whether or not information on the lower delay time between the antenna station-accommodated in the aggregation station-and the fronthaul multiplexeris registered. When the information on the lower delay time between the antenna station-accommodated in the aggregation station-and the fronthaul multiplexeris registered, the delay time management unitacquires the insertion delay time by using the registered information on the lower delay time.

10 FIG. 10 30 10 1 55 10 1 30 10 3 40 3 30 b b b. For example, in the example shown in, the antenna stationconnected to the fronthaul multiplexeris only the antenna station-. Thus, the delay time management unitacquires the insertion delay time so as to become the same delay on the basis of the lower delay time between the antenna station-and the fronthaul multiplexerand the lower delay time between the antenna station-accommodated in the aggregation station-and the fronthaul multiplexer

55 30 10 55 10 1 10 3 55 b 9 FIG. The delay time management unitnotifies the fronthaul multiplexerof the acquired information on the insertion delay time and information for specifying the antenna stationto be connected from now. For example, when acquiring the insertion delay time so as to be 100 us as shown in, the delay time management unitacquires 85 us (=100 us−15 us) as the insertion delay time for the antenna station-, and acquires 50 us (=100 us−50 us) as the insertion delay time for the antenna station-. In this way, the delay time management unitdetermines the total value of the lower delay time and the insertion delay time and acquires the insertion delay time by subtracting the lower delay time from the determined total value.

33 30 10 50 33 50 31 20 33 10 1 10 3 b b b The switching notification receiving unitof the fronthaul multiplexergrasps the antenna stationto be connected from now on the basis of the information transmitted from the controller. Further, the switching notification receiving unitsets information on the insertion delay time corresponding to each of the antennas obtained from the controllerto the lower-side delay insertion unitat the timing when the switching of the optical distribution unitis performed. For example, the switching notification receiving unitis set to impart the delay of 85 us to the uplink signal transmitted from the antenna station-, and set to impart the delay of 50 us to the uplink signal transmitted from the antenna station-.

53 40 3 54 40 3 4 20 54 10 3 40 3 4 20 When the sleep detection unitdetects the migration of the aggregation station-to the sleep state, the switching signal transmission unitrefers to the optical distribution unit connection table to grasp that the aggregation station-is connected to the second port uof the optical distribution unit. Further, the switching signal transmission unitgrasps that the antenna station-accommodated in the aggregation station-is connected to the first port dof the optical distribution unit.

54 10 3 40 1 2 20 40 1 40 3 54 4 20 4 20 4 20 2 20 54 20 20 4 2 10 FIG. Thereafter, the switching signal transmission unitrefers to the items of the port used at sleep and the aggregation station used at sleep in the optical distribution unit connection table to grasp that the connection destination of the antenna station-is the aggregation station-and utilization of the second port uof the optical distribution unittoward the aggregation station-when the aggregation station-is asleep. Therefore, the switching signal transmission unitgenerates the switching signal that instructs to switch the connection connected from the first port dof the optical distribution unitto the second port uof the optical distribution unitto a connection connected from the first port dof the optical distribution unitto the second port uof the optical distribution unit. The switching signal transmission unittransmits the generated switching signal to the optical distribution unit. Therefore, the optical distribution unitswitches the connection so as to connect the first port dand the second port uas shown by a dotted line in.

20 33 30 31 10 1 31 10 3 10 1 10 3 30 32 b b Following the switching of the connection relation of the optical distribution unit, the switching notification receiving unitof the fronthaul multiplexersets the lower-side delay insertion unitso as to impart the delay of 85 us to the uplink signal transmitted from the antenna station-and sets the lower-side delay insertion unitso as to impart the delay of 50 us to the uplink signal transmitted from the antenna station-. With such settings, the above-described delays are imparted to the uplink signals transmitted from the respective antenna stations-and-in the fronthaul multiplexer. As a result, the time point is adjusted and the signal merging unitgenerates the multiplex signal.

100 31 10 54 30 30 10 20 31 b b b In the conventional technique, when a new antenna station is connected, the fronthaul multiplexer measures a propagation delay time between the fronthaul multiplexer and the newly connected antenna station and inserts a delay in the lower-side delay insertion unit so as to match the timing at which an uplink signal from another antenna station is transmitted to the aggregation station. On the other hand, according to the communication systemaccording to the third embodiment, the lower-side delay insertion unitacquires the delay time (insertion delay time) to be imparted to the uplink signal of the newly connected antenna stationon the basis of information on the lower delay time received from the switching signal transmission unitby the fronthaul multiplexer. For this, in the fronthaul multiplexer, when the antenna stationis newly connected by switching the optical distribution unit, the appropriate insertion delay time is determined without performing delay measurement, and the delay can be imparted by the lower-side delay insertion unit. For this, the switching can be completed in a shorter time. As a result, the occurrence of packet loss can be suppressed or the occurrence of packet loss can be prevented.

50 20 20 100 60 65 50 60 40 65 60 51 52 b b b In the above-mentioned embodiment, the controllerdetermines whether or not to allow sleep and issues the switching instruction to the optical distribution unit. It may be configured to determine whether or not to allow the sleep and issue the switching instruction to the optical distribution unitby different devices. When configured in this way, the communication systemaccording to the third embodiment includes a radio controllerand an optical distribution unit controllerin place of the controllersimilarly to the modification example of the first embodiment. The radio controllerperforms radio communication with the aggregation stationand with the optical distribution unit controller. The radio controllerincludes an acquisition unitand a sleep control unit.

51 60 40 51 40 51 40 52 52 60 40 40 51 The acquisition unitincluded in the radio controlleracquires the determination information from each of the plurality of aggregation stationsby radio. The acquisition unitacquires the determination information from each of the plurality of aggregation stationsat predetermined timing or periodically by radio, for example. The acquisition unitoutputs the acquired determination information of each aggregation stationto the sleep control unit. The sleep control unitincluded in the radio controllerdetermines whether or not the aggregation stationcan be asleep on the basis of the determination information of each aggregation stationacquired by the acquisition unit.

52 65 52 When determined to allow sleep, the sleep control unitnotifies the optical distribution unit controllerthat the sleep target aggregation station is made asleep by radio. Further, when determined to allow sleep, the sleep control unittransmits the sleep instruction to the sleep target aggregation station by radio.

65 20 65 53 54 55 53 65 60 53 54 65 20 20 54 The optical distribution unit controllercontrols the optical distribution unit. The optical distribution unit controllerincludes a sleep detection unit, a switching signal transmission unit, and a delay time management unit. The sleep detection unitincluded in the optical distribution unit controllerdetects the migration of the sleep target aggregation station to the sleep state in response to the notification from the radio controller. When the sleep detection unitdetects the migration of the sleep target aggregation station to the sleep state, the switching signal transmission unitincluded in the optical distribution unit controllertransmits the switching signal to the optical distribution unit. The switching operation of the optical distribution unitby the switching signal transmission unitis the same as the method shown in the third embodiment.

53 55 65 55 When the sleep detection unitdetects the migration of the sleep target aggregation station to the sleep state, the delay time management unitincluded in the optical distribution unit controlleracquires information on the lower delay time corresponding to the switching target antenna station. The processing performed by the delay time management unitis the same as that in the third embodiment.

100 100 20 b b The communication systemmay be configured to release the sleep of the sleeping aggregation station similarly to the second embodiment. Further, when configured to release the sleeping aggregation station, the communication systemmay be configured to determine whether or not the sleep release is required and issue the switching instruction to the optical distribution uniton different devices similarly to the modification example of the second embodiment.

40 40 The aggregation stationmay be a virtualized aggregation station. Therefore, the information processing device having the virtualization function can be used, and the above-described processing can be realized even if it is not on a dedicated device.

30 30 50 50 b b At least some or all of each functional unit of the fronthaul multiplexerand, and the controllerandare realized as software by a processor such as a CPU (Central Processing Unit) executing a program stored in a storage device and a storage unit having a non-volatile recording medium (non-transitory recording medium). The program may be recorded on a computer-readable non-transitory recording medium. The computer-readable non-transitory recording medium is a non-temporary recording medium such as a portable medium such as a flexible disk, a magneto-optical disc, a ROM (Read Only Memory), or a CD-ROM (Compact Disc Read Only Memory), or a storage device such as a hard disk built into a computer system, for example.

30 30 50 50 b b At least some or all of each functional unit of the fronthaul multiplexerandor some or all of each functional unit of the controllerandmay be realized using hardware including electronic circuits (electronic circuit or circuitry) using, for example, an LSI (Large Scale Integrated circuit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), an FPGA (Field Programmable Gate Array), or the like.

Although the embodiment of the present invention has been described in detail with reference to the drawings above, a specific configuration is not limited to this embodiment, and design within the scope of the gist of the present invention, and the like are included.

The present invention is applicable to a communication system including a fronthaul multiplexer.

10 10 1 10 3 ,-to-Antenna station 20 Optical distribution unit 30 30 b ,Fronthaul multiplexer 31 31 b ,Lower-side delay insertion unit 32 Signal merging unit 33 Switching notification receiving unit 40 40 1 40 3 ,-to-Aggregation station 50 50 b ,Controller 51 Acquisition unit 52 Sleep control unit 53 Sleep detection unit 54 Switching signal transmission unit 55 Delay time management unit 60 Radio controller 65 Optical distribution unit controller 100 Communication system